1. Field of the Invention
The present invention relates to a resist composition. More particularly, the present invention relates to a positive composition which is particularly suitable for the formation of very fine patterns on a substrate having a high reflectance such as an aluminum plate in the production of a semiconductive device such as IC or LSI.
2. Background of the Invention
Hitherto, in the production of an integrated circuit such as LSI, a resist composition comprising a quinone diazide type sensitizer and a novolak resin or comprising a bisazide type sensitizer and a cyclic rubber base resin is used.
In the production of the integrated circuit, fine patterns are drawn on various substrates through a resist composition. On a substrate having a high reflectance such as a substrate made of aluminum, aluminum-silicon or polysilicon, a conventional resist composition is sensitized in a region in which the composition should not be sensitized with reflected light from a substrate surface and/or side walls of stepped parts, resulting in notching or halation.
To overcome the above drawback and prevent deterioration of resolution, Japanese Patent Publication No. 7562/1976 proposes a resist composition comprising a dye of the formula: ##STR3## (Oil Yellow, C.I.-11020) as a light absorber. By this dye, an amount of light which passes through a resist layer is greatly decreased and an amount of stray light to a light-shielded area is decreased.
However, by the addition of the light absorber, a sensitivity of the resist composition is, in general, greatly decreased so that productivity of the semiconductors is undesirably decreased.
Usually, in the formation of a resist film, the resist composition containing a solvent is coated on a wafer and then the coated wafer is prebaked to remove the solvent. Some light absorbers deposit during storage of the resist composition, or sublimates during prebaking, so that resist performances tend to vary.